An internal combustion engine having an exhaust gas recirculation device (hereinafter, this device will be referred to as—EGR device—) is described in the Patent Document 1. This EGR device supplies (i.e. re-circulates) an exhaust gas into a combustion chamber of the engine by introducing in an intake passage an exhaust gas discharged from the combustion chamber to an exhaust passage. Below, the exhaust gas supplied in the combustion chamber by the EGR device will be referred to as—EGR gas—and an amount of the EGR gas supplied into the combustion chamber will be referred to as—EGR gas amount—.
The EGR device described in the Patent Document 1 has an EGR control valve. This EGR control valve is constituted such that its opening degree can be changed. The EGR gas amount can be controlled by controlling the opening degree of the EGR control valve. Then, the EGR gas decreases an amount of a substance (in particular, nitrogen oxide) produced by combustion of a fuel in the combustion. That is, the EGR gas decreases an exhaust gas emission discharged from the combustion chamber.
The EGR gas amount for optimally decreasing the exhaust gas emission depending on the engine operation condition (i.e. the operation condition of the engine). In the engine described in the Patent Document 1, the EGR gas amounts for optimally decrease the exhaust gas emission depending on the engine operation condition are previously obtained by an experiment, etc., these obtained EGR gas amount are memorized in an electronic control device of the engine as target EGR gas amounts, the target EGR gas amount is acquired depending on the engine operation condition from the target EGR gas amounts memorized in the electronic control device during the engine operation (i.e. during the operation of the engine) and the opening degree of the EGR control valve is controlled such that the actual EGR gas amount corresponds to this acquired target EGR amount.